The purpose of this competing renewal application is to continue, expand and merge the Biliary Atresia Research Consortium (BARC) and the Cholestatic Liver Consortium (CLiC) to form the Childhood Liver Disease Research and Education Network (ChiLDREN). ChiLDREN will have as its overall objectives to further define the epidemiology, clinical features, and pathophysiology of the major cholestatic liver diseases afflicting children, and develop new therapies to improve and prolong the life of these patients. The proposal consists of the following Specific Aims: Aim 1) Continue with the work of the Biliary Atresia Research Consortium: a) the trial of corticosteroids post portoenterostomy, b) acquire new information on epidemiology, clinical features, factors affecting outcome post portoenterostomy, and histopathology of biliary atresia, c) define the role of modifier genes in influencing outcome, and d) develop new therapies to attenuate or prevent the development of biliary cirrhosis post portoenterostomy; Aim 2) Study the natural history, clinical features, the correlation of genotype with phenotype, and prognosis of inherited forms of intrahepatic cholestasis including Alagille syndrome, alpha-1-antitrypsin deficiency, progressive familial intrahepatic cholestasis (PFIC), and bile acid synthesis defects; and Aim 3) Determine overall frequency, full clinical spectrum and natural history of the mitochondrial hepatopathies. For all studies a repository of serum, urine, tissue, and DNA specimens will be available for use in future ancillary studies. The infrastructure and collaborations within ChiLDREN offer unique training opportunities for young investigators. Small pilot grants and demonstration projects will allow new hypotheses to be tested that could lead to more substantial funding from the National Institutes of Health through an independent grant or a larger study involving all of the ChiLDREN centers. There is also a need to increase public awareness about pediatric liver disease to primary care physicians and the lay public through our publications and website. Relevance: Biliary atresia and a group of inherited cholestatic syndromes remain poorly understood, and are associated with significant morbidity, mortality, and need for liver tranplantation. The ChiLDREN program will produce new knowledge on the clinical features and causes of these diseases, and develop therapies to improve and prolong the life of these patients.